1. Field of the Invention
The present invention relates to alpha-amylase variants, polynucleotides encoding the variants, methods of producing the variants, and methods of using the variants.
2. Description of the Related Art
Alpha-amylases (E.C. 3.2.1.1) constitute a group of enzymes which catalyze hydrolysis of starch, glycogen and related polysaccharides and oligosaccharides.
Alpha-amylases are used commercially for a variety of purposes such as in the initial stages of starch processing (e.g., liquefaction); in wet milling processes; and in alcohol production from carbohydrate sources. They are also used as cleaning agents or adjuncts in detergent matrices; in the textile industry for starch desizing; in baking applications; in the beverage industry; in oil fields in drilling processes; in recycling processes, e.g., for de-inking paper; and in animal feed.
Some commercial alpha-amylases for, e.g., starch liquefaction originate from Bacillus licheniformis or Bacillus stearothermophilus. Protein engineered variants of wild type enzymes have been developed to overcome process issues. There is still a need, though, for novel alpha-amylases with improved properties, such as higher stability at low pH, low calcium and high temperature. Such enzymes will allow the starch liquefaction process to be run at reduced pH which has a positive influence on chemical savings.
It is an object of the present invention to provide novel alpha-amylase variants having an increased stability at low pH and/or at high temperature, in particular at low calcium concentrations.